Thermally assisted magnetic recording (TAMR) is expected to facilitate magnetic recording at a 1˜10 Tb/inch2 data density. TAMR converts optical power into highly localized heating in a magnetic recording medium so as to temporarily reduce the field needed to switch the magnetizations of the medium grains. The steep temperature gradient (alone or together with an already-present high magnetic field gradient) enables data storage density to be improved beyond what can be achieved by current state-of-the-art magnetic recording technologies.
A TAMR head, in addition to the standard magnetic recording components, usually comprises a wave-guide (WG) and a Plasmon antenna (PA) or Plasmon generator (PG). The WG acts as an intermediate path to guide the externally generated laser light to the PA or PG, where the WG's optical mode is coupled to the local Plasmon mode of the PA or to the propagating Plasmon mode of the PG. The optical energy, after being converted to Plasmon energy, either through local Plasmon excitation in the PA or through energy transmission along the WG, now has a substantially higher frequency than it had when it emerged from the LD. As a result, its concentration at the location where heating of the media is desired in order to achieve TAMR is no longer diffraction limited.
Prior art proposals [1-2] describe a head structure of the type illustrated in FIGS. 1a and 1b for the achievement of TAMR. FIG. 1a is a cross-sectional view while FIG. 1b is an air bearing surface (ABS) view. Shown there are read head 1, plasmon antenna (or generator) 2, wave-guide 3, perpendicular write pole 4, and laser diode (LD) 5, that is mounted on the top of the slider. And field coils 6. The laser beam exits laser diode 4 and couples directly into WG 3. The PG is used to excite the Edge Plasmon (EP) mode, which confines the energy to the end of the sharp tip since it is no longer subject to optical diffraction effects.
There are, however, some serious limitations associated with these prior art designs. For example, a specially designed suspension and bonding pads are required to mount the LD on the slider. The ‘end fire’ coupling method (butted ends with no intermediate focusing aids) is typically used to directly couple the laser beam from the LD into the waveguide. This method has low efficiency because of the divergent nature of the beam that emerges from the LD. Also, the precise alignment that is needed between the LD and the wave-guide means that assembly and packaging become unappealingly expensive.    [1] K. Tanaka, K. Shimazawa, and T. Domon, “Thermally assisted magnetic head,” US Patent Pub. #US 2008/0192376 A1 (2008)    [2] K. Shimazawa, and K. Tanaka, “Near-field light generator plate, thermally assisted magnetic head, head gimbal assembly, and hard disk drive,” US Patent Pub. #US2008/0198496 A1 (2008)A routine search of the prior art was performed with the following additional references of interest being found:
In U.S. Pat. No. 7,365,941, Poon et al. disclose an optical head including a laser beam directing mirror and a beam-focusing lens. Van Kesteran, in U.S. Pat. No. 6,873,576, teaches that laser light is preferably focused on a disk by an optical lens via a mirror while US 2008/0316872 (Shimizu et al.) shows a lens and mirror in conjunction with a waveguide.
Gomez et al. disclose a lens to emit a collimated beam in US 2008/0123219 while Matsumoto shows a collimator lens, to focus light exiting from a waveguide, in US 2008/0117727. In US 2006/0256694, Chu et al. show a focusing lens, a steerable mirror, and a waveguide while Rausch et al. disclose a lens, waveguide, and curved or straight mirror in US 2006/0233061.